1. Lesson Overview Lesson Overview The Circulatory System Objectives 33.1 The Circulatory System -Identify the functions of the human circulatory system. -Describe the structure of the heart and how it pumps blood through the body. -Name three types of blood vessels in the circulatory system.

2. Lesson Overview Lesson Overview The Circulatory System What does the Circulatory System do? The circulatory system transports oxygen, nutrients and other substances throughout the body, and removes wastes from tissues.

3. Lesson Overview Lesson Overview The Circulatory System Heart Structure Your heart is composed almost entirely of a muscle layer called myocardium. The heart begins beating 18 days after conception and stops only when you die. An adult’s heart beats an average 72x a minute, pumping about 70 milliliters (about 2.5 cups) of blood with each contraction.

4. Lesson Overview Lesson Overview The Circulatory System Heart Structure The heart is divided into four chambers. 1.Two upper chambers called atria (singular: atrium); 2.Two lower chambers called ventricles. A wall called the septum separates the right side of the heart from the left side.

5. Lesson Overview Lesson Overview The Circulatory System Blood Flow Through the Heart Flaps of tissue called valves are located between the atria and the ventricles; as well as, at the exits of each ventricle. Valves prevent the back flow of blood.

6. Lesson Overview Lesson Overview The Circulatory System The Heart’s Blood Supply The heart muscle needs a constant supply of oxygen and nutrients. A pair of blood vessels called coronary arteries supply blood to the heart muscle.

7. Lesson Overview Lesson Overview The Circulatory System Circulation The heart functions as two pumps. 1.The right side of the heart pumps blood to the lungs; pulmonary circulation. 2.The left side pumps blood to the rest of the body; systemic circulation.

8. Lesson Overview Lesson Overview The Circulatory System The “Pacemaker” Each contraction begins in a small group of muscle fibers called the SA node, located in the right atrium. The SA node “sets the pace” for the heart, so it is referred to as the pacemaker.

9. Lesson Overview Lesson Overview The Circulatory System Blood Vessels Blood flows through three types of vessels — arteries, capillaries, and veins.

10. Lesson Overview Lesson Overview The Circulatory System Arteries Arteries are large vessels that carry blood away from the heart to the rest of the body. Arteries have thick elastic walls that help them withstand the powerful pressure produced when the heart contracts.

11. Lesson Overview Lesson Overview The Circulatory System Capillaries The smallest blood vessels are the capillaries. Most capillaries are so narrow that blood cells pass through them in single file. The extremely thin walls allow O 2, nutrients, CO 2 and waste to diffuse across their walls.

12. Lesson Overview Lesson Overview The Circulatory System Veins After blood passes through the capillaries, it returns to the heart through veins. Veins also contain valves that close to ensure blood does not flow backward.

13. Lesson Overview Lesson Overview The Circulatory System Blood Pressure Blood pressure is measured with the following two numbers: 1. Systolic pressure — the force in the arteries when the ventricles contract. 2. Diastolic pressure — the force in the arteries when the ventricles relax. * A typical blood pressure reading for a healthy teen or adult is below 120/80.

14. Lesson Overview Lesson Overview The Circulatory System True or False The nervous system transports oxygen, nutrients, and other substances around the body. ______________________________ After the AV node produces impulses, blood flows into the ventricles, which contract. _________________________

15. Lesson Overview Lesson Overview The Circulatory System Answers The nervous system transports oxygen, nutrients, and other substances around the body. False, circulatory After the AV node produces impulses, blood flows into the ventricles, which contract. True